Найти путь в ориентированном графе - Prolog

Welcome to SWI-Prolog (Multi-threaded, 32 bits, Version 5.10.2)
Copyright (c) 1990-2010 University of Amsterdam, VU Amsterdam
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.
 
For help, use ?- help(Topic). or ?- apropos(Word).
 
?- ['find'].
% find compiled 0.00 sec, 1,432 bytes
true.
 
?- find(a,3,X).
X = [a, c] ;
false.
 
?- find(a,4,X).
X = [a, c, e] ;
X = [a, d] ;
false.
 
?- find(a,5,X).
X = [a, c, e, f] ;
X = [a, d, e] ;
false.
 
?- find(a,6,X).
X = [a, d, e, f] ;
false.
 
?- find(a,7,X).
false.
 
?-